There are widely known rotatable apparatus systems including a prime mover and a driven apparatus as a rotatable apparatus to be driven by the prime mover. For example, there are known pump systems including a motor as one example of the prime mover, and a pump as one example of the rotatable apparatus (the driven apparatus). In the pump systems, a main shaft of the pump is coupled to a main shaft of the motor via a shaft coupling, and the pump rotates by being driven by the motor. The shaft coupling rotates at a high speed, and therefore, generally, a shaft coupling guard is mounted around the shaft coupling to prevent a human from touching a rotating portion and a foreign object from entering therein.
Conventionally, mostly, the shaft coupling guard has been provided as a simple member that covers the shaft coupling with an arch-like (tunnel-like) structure. This arch-shaped shaft coupling guard can realize covering of the shaft coupling by an easy mounting process. However, on the other hand, this shaft coupling guard has wide arch-shaped openings at the both sides in an axial direction.